1. Field of the Invention
The present invention relates to a recording apparatus, and more particularly to an ink supplying system.
2. Description of the Related Art
Since an inkjet recording apparatus for forming an image on a recording medium by applying liquid ink to the recording medium by, for example, an inkjet recording head serving as a device which uses a liquid can form small dots close together with a relatively low noise level during recording, the inkjet recording apparatus is nowadays used in many types of recording operations, such as color image recording operations. One type of such an inkjet recording apparatus comprises an inkjet recording head, a carriage, and transporting means. The inkjet recording head receives ink from an integrally and inseparably or separably mounted ink tank. The carriage allows the recording head to perform a main scanning operation in a predetermined direction with respect to a recording medium by carrying the recording head. The transporting means transports the recording medium in a direction perpendicular to the main scanning direction so as to carry out a sub-scanning operation. The inkjet recording apparatus performs a recording operation on the recording medium by discharging ink during main scanning by the recording head. When a recording head, which can discharge black ink and color ink (such as yellow, cyan, and magenta ink), is mounted on the carriage, not only can monochromatic recording of a text image using black ink be carried out, but also full-color recording of an image can be carried out by changing the proportion of discharge of each ink.
A very small ink path is formed in the inkjet recording head. Any ink to be supplied to the recording head from the ink tank is required to be clean without any foreign matter, such as dust. If the ink contains any foreign matter, the foreign matter gets stuck in the ink path in the recording head, particularly, in a narrow discharge opening and a liquid path portion that directly communicates with the discharge opening. Therefore, it may be impossible to restore functions of the recording head.
To overcome this problem, in general, a structure for preventing entry of foreign matter into the recording head by a filter for removing any foreign matter is often used in the ink path between the recording head and an ink supply needle inserted in the ink tank.
Nowadays, in order to increase recording speed, the number of discharge openings of the inkjet recording head for discharging ink is increased, or drive signals of higher frequency are applied to a device for generating energy for discharging ink. Therefore, the amount of ink consumed per unit time is sharply increased, thereby obviously increasing the amount of ink passing through the filter. An effective way of reducing pressure loss by the filter is to form the filter with a large area by enlarging part of an ink supply path. However, when gas bubbles enter the ink supply path, the gas bubbles tend to be retained in a space at an upstream side of the filter at the enlarged portion of the ink supply path. Therefore, when these gas bubbles cannot be discharged, ink may not be smoothly supplied. In addition, gas in the ink supply path becomes minute gas bubbles that can mix with the ink that is guided to the discharge openings of the recording head. This may, for example, prevent ink discharge from the recording head. To overcome this problem, in such an inkjet recording apparatus, it is important not to allow gas, such as air, to be introduced into the ink supply path. The main reason for gas to flow into an ink supply system is, for example, depletion of ink in the ink tank and replacement of the ink tank.
Related replaceable ink tanks are ink tanks having a storage medium for holding information on the amount of ink in the ink tank, as disclosed in U.S. Pat. No. 5,699,091, an ink tank that is not capable of detecting ink, and an ink tank capable of detecting depletion of ink in the ink tank as disclosed in Japanese Patent Laid-Open No. 2001-162820.
As disclosed in U.S. Pat. No. 5,699,091, in order to minimize the introduction of gas, such as air, into the ink supply path of the inkjet recording apparatus, ordinarily, a user is prompted to replace the ink tank by stopping the recording apparatus having a predetermined amount of ink left in the ink tank after being informed of the residual ink amount in the ink tank based on the ink amount information held by the storage medium. As disclosed in Japanese Patent Laid-Open No. 2001-162820, ordinarily, the ink tank detects depletion of ink by, for example, optically detecting the residual ink amount by using a prism and an optical sensor or by detecting the residual ink amount by making use of a change in the electrification resistance between two electrode pins. Both of these methods are used to detect whether or not the residual ink amount has reached a predetermined amount. Since there may be an error in detecting the residual ink amount caused by the introduction of gas, such as air, into the ink supply path of the inkjet recording apparatus, the user is informed of the running out of ink with a predetermined amount of ink remaining in the ink tank.
Therefore, the ink tank disclosed in this patent document is discarded before the ink in the ink tank is used up.
The user determines the residual ink amount in the ink tank that is not capable of detecting ink on his own. Therefore, when the ink in the recording head in addition to that in the ink tank and the ink supply path is used up, and a recording image starts to get blurred, the user determines that the ink tank has run out of ink, and, thus, replaces the ink tank.
In the replacement of these replaceable ink tanks, the ink supply path at the recording head and a connection opening of the ink tank are temporarily separated. Therefore, air may enter the ink supply path. The air in the ink supply path may be removed by the following cleaning operation.
First, a surface of the recording head in which a discharge opening is formed (discharge opening side) is covered with a cap, and a suction pump is driven at a high speed in order to produce a negative pressure in the cap. This causes a large negative pressure to act upon the capped discharge opening side and a high ink flow rate to be produced in the discharge opening direction from the inside of the ink supply path, causing retained air bubbles to be sucked and discharged from the discharge opening along with the ink. However, in order to sufficiently remove the gas by this method, a large amount of ink needs to be sucked and discharged. Therefore, a corresponding amount of ink is wasted.
As mentioned above, the related ink tanks are discarded before all of the ink in the ink tanks is used up. Therefore, a large amount of ink that can actually be used is wastefully discharged by the cleaning operation. In addition, when the cleaning operation is being carried out, the body of the recording apparatus cannot carry out a recording operation. Therefore, the user wastes time because he/she cannot carry out a recording operation until the cleaning operation ends. Further, a suction pump mechanism for carrying out the cleaning operation and a waste ink receiver for accommodating the sucked ink are required, thereby increasing costs and the size of the recording apparatus body accordingly.